Within the scope of minimally-invasive surgery, such as endoscopic or laparoscopic surgery, access to the operating site is made via small incisions in the body of the patient (such as the abdomen or thorax), in which the practitioner places a cannula formed by a tube whereof the diameter varies from 3 to 15 mm, via which the practitioner can insert into the body of the patient either an endoscope for obtaining a video image on a monitor, or long and fine instruments for performing a procedure at the operating site.
The majority of existing instruments is constituted by a fine (typically around 5 mm in diameter) and rigid elongated body (typically around 30 cm long). The proximal end of the instrument comprises a grip handle for the practitioner and the distal end of the instrument is often fitted with a forceps or scissors, optionally capable of transmitting electric current for cutting (monopolar or bipolar).
The main advantage of laparoscopic surgery is the minimum incisions. However, the main limitation is the decrease in dexterity associated with a remote access by long instruments. Indeed, when the instrument is rigid, its passage via a fixed incision point is a planar kinematic constraint which limits the number of degrees of freedom (DoF) to four, i.e. three movements of rotation about the point of incision and a penetration translation movement of the instrument. In particular, with conventional laparoscopic rigid instruments, it is impossible to bend the distal end of the instrument to orient the forceps optimally relative to the practitioner. This is a major application limitation of laparoscopic surgical tools for surgical procedures.
This has led to the development of novel instruments comprising a distal part exhibiting mobility relative to the principal body of the instrument. For example, for suturing exercise, the surgeon uses a curved needle. When he carries out this exercise in optimal conditions, the surgeon:                1. grasps the needle such that the plane of the needle is perpendicular to the axis of the forceps;        2. places the plane of the needle perpendicularly to the edges to be sutured;        3. turns the needle according to an axis perpendicular to its plane to insert it into the tissue to be sutured.        
Therefore, to make a suture in favorable conditions, there must be means for placing the axis of the instrument substantially parallel to the edges to be sutured and turning the forceps about its axis. During some interventions, positioning the points of incision relative to the operating site is such that it is not possible to align the axis of the forceps with the edges to be sutured when using rigid instruments, substantially complicating the way to make the suture. Thus instruments have been developed which are adapted for orienting the axis of the forceps relative to the principal axis of insertion of the instrument in the body, due to distal mobility.
It should be noted that the final rotation movement of the forceps around its own axis (intrinsic rotation of the forceps), which controls penetration of the needle, must be made with a high precision and a maximal stability of the direction of the axis of the forceps while applying sufficient force to perforate tissue.
There have been a lot of different developments of surgical instruments having a distal mobility. Generally, these surgical instruments are such that the axis of the forceps can be oriented relative to the main axis of insertion of the instrument through a rotation made about any axis perpendicular to such main axis of insertion. These instruments may be supported by a robotic arm but are more often hand held.
With these kind instruments, the user further wants to be able to orient the axis of the forceps in any direction relative to the main axis of insertion of the instrument. This requires that the forceps is mounted with two orthogonal pivot joints on the instrument shaft and that each pivot joint has a 180° range of motion to provide a right angle orientation of the forceps in both directions. Instruments fulfilling this requirement have for instance been described in U.S. Pat. Nos. 7,147,650, 7,338,513, 7,686,826, 7,842,028, US2006111210, US2007250113, US2010286480, or US2010331860. However the more complex the joint between the forceps and the instrument shaft, the bigger the joint. Moreover overall instrument diameter is an issue in minimally invasive surgery where 5 mm diameter is a gold standard. Some have chosen to use flexible material in between shaft and forceps to reduce joint diameter, but it then compromises overall strength and rigidity. Further, most of the proposed solutions can unfortunately not be adapted for motorization of the motion of the forceps—or any other distal tool—which is a major drawback since motion of such distal tool generally need to be very accurate.
In WO2010112608 and WO2010112609, is described an instrument having a forceps mounted on an outer arm comprising a pivot joint around a single axis. This enables using assembly element such as vertebrae which provide a good resistance to forces applied off the plane that is perpendicular to the pivot axis. Also, when the instrument is motorized, using one pivot only exhibits the advantage of requiring only one actuator dedicated to the orientation of the forceps. However as described above, this does not allow to orient forceps in any direction.
A solution to overcome this problem is to use a further rotation around the insertion axis. This rotation can for instance be manually controlled by the surgeon at the handle level. However, a drawback to this hand rotation is the limited range of possible rotation, induced by the limited range of human wrist motion. When handling an instrument handle, it can be considered that the maximum range of rotation is 180° degrees, which is the range of the pronation-supination wrist motion. If a 360° rotation is required, it may be used the instrument described in WO2011013100 that comprises a handle and control means with a cylindrical symmetry, which enables the user to rotate the instrument in its hand and to still be able to use instrument normally (no preferential orientation). However, manipulating such an inline instrument imposes the user to put elbow up which involves shoulder abduction. This anatomical posture is known not to be ergonomic in the long run.
In US2010249497 it has been proposed two different embodiments of a surgical instrument provided with means to orbit the distal tool relative to the longitudinal axis of the main shaft, said orbit of the distal tool being made by an own rotation of the instrument shaft. The first embodiment which is disclosed in this document is fully manually operated, with only mechanical coupling. In particular, there is proposed to use a mechanical ball & neck assembly for manually actuating the bending of the distal tool. The second embodiment disclosed in US2010249497 comprises a motorized push/pull cable drive mechanism that replaces the ball & neck assembly. The motorized assembly does however complexify the structure of the surgical instrument. In particular, an own rotation of the distal tool can only be operated by combination of the pivot and orbit movements of the tool, more precisely a combination of the own rotation of the instrument shaft and two pivots of the distal tool made about two axis perpendicular to the longitudinal axis of the instrument and perpendicular to each other. However, such combination of movements necessarily requires an electronic control of the corresponding motors, which complexifies the instrument. Such surgical instrument has further the drawback of being relatively voluminous, when full motorization is used.
A goal of the present invention is thus to propose a surgical instrument that does not present the above drawbacks.
More precisely, a goal of the present invention is to propose a surgical instrument that enables the distal tool to have any desired position, where control of the motion of the distal tool being very accurate, and which manipulation is easy and comfortable for the surgeon.
Another goal of the present invention is to propose a surgical instrument with an innovative actuation mechanism of the bending motion of the distal tool.